Enthalpies of reaction of zirconium and molybdenum tetrachlorides with pyridine, tetrahydrofuran, and tetrahydrothiophene

Enthalpies of addition were determined calorimetrically for the crystalline complexes MCl4•2L where M = Zr and L = pyridine or M = Mo and L = pyridine, tetrahydrofuran, or tetrahydrothiophene. Molybdenum(IV) is a significantly better acceptor than zirconium(IV) toward pyridine and tetrahydrofuran but not toward tetrahydrothiophene. A possible explanation for this is discussed.